Condensed Consolidation Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017		Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 71,631		$ 80,100		$ 14,083		$ 33,165
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment (1)	1,881	[1]	(1,693)	[1]	4,779	[2]	(599)	[2]
Defined benefit retirement plan (2)	128	[3]	151	[3]	257	[4]	302	[4]
Change in cash flow hedging (3)	96	[5]	(3)	[5]	310	[6]	(395)	[6]
Other comprehensive income (loss), net of tax	2,105		(1,545)		5,346		(692)
Comprehensive income	73,736		78,555		19,429		32,473
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	(19,605)		(19,213)		(19,605)		(19,213)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	54,131		59,342		(176)		13,260
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	1,000		(900)		2,600		(300)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	(100)		(100)		(200)		(200)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	$ 100		$ 0		$ 200		$ (300)

[1] Foreign currency translation adjustment is presented net of tax expense of $1.0 million and net of tax benefit of $0.9 million for the three months ended June 30, 2017 and June 30, 2016, respectively.

[2] Foreign currency translation adjustment is presented net of tax expense of $2.6 million and net of tax benefit of $0.3 million for the six months ended June 30, 2017 and June 30, 2016, respectively.

[3] Defined benefit retirement plan is presented net of tax expense of $0.1 million for each of the three months ended June 30, 2017 and June 30, 2016, respectively.

[4] Defined benefit retirement plan is presented net of tax expense of $0.2 million for each of the six months ended June 30, 2017 and June 30, 2016

[5] Change in cash flow hedging is presented net of tax expense of $0.1 million for the three months ended June 30, 2017 and net of a nominal tax benefit for the three months ended June 30, 2016.

[6] Change in cash flow hedging is presented net of tax expense of $0.2 million for the six months ended June 30, 2017 and net of tax benefit of $0.3 million for the six months ended June 30, 2016.